1. Field of the Invention
This invention relates generally to laser devices. More particularly, the present invention relates to a laser device of the type which utilizes a semiconductor laser chip sealed in a molded body.
2. Description of the Prior Art
A semiconductor laser chip used in a laser device is known to be adversely affected by humidity or other external factors. Therefore, it has been conventionally proposed to enclose the semiconductor laser chip in a resinous molded body for protection. This type of laser device is called "mold-type semiconductor laser device" and disclosed in Japanese Patent Application Laid-open No. 64-28882 for example.
For the convenience of explanation, reference is now made to FIGS. 23 and 24 which illustrate a prior art mold-type semiconductor laser device.
As shown in FIGS. 23 and 24, the prior art laser device comprises a metallic support plate 21 integral with a first lead 22. A mount 23 is attached on the support plate 21, and a semiconductor laser chip 24 is attached on the mount 23. The laser chip 24 has a front cleavage face 24' for emitting a coherent output laser beam E".
The first lead 22 is flanked by second and third leads 25, 26, and the laser chip 24 together with the support plate 21 and the mount 23 is enclosed in a transparent resinous molded body 27 with the respective leads 22, 25, 26 projecting partially from the molded body 27. A glass plate 28 is attached to the molded body 27 in opposed relation to the front cleavage face 24' of the laser chip, so that the output laser beam E" passes through the glass plate.
In such a laser device, it is known that the laser beam emission performance is influenced by the spacing L (see FIG. 24) between the glass plate 28 and the front cleavage face 24' of the laser chip 24. Further, the laser beam emission performance is also affected by the orientation of the glass plate 28 relative to the front cleavage face 24' of the laser chip 24. Thus, it is necessary to appropriately select the spacing L and orientation of the glass plate 28 in relation to the laser chip 24.
However, with the arrangement of the prior art laser device, the glass plate 28 is attached only to the molded body 27, so that the position and orientation of the glass plate 28 relative to the laser chip 24 is influenced by dimensional errors of the molded body 27. Thus, even if the laser chip 24 is accurately mounted on the support plate 21, the position and orientation of the glass plate 28 will be inappropriate when the molded body 27 is formed improperly, consequently resulting in deterioration of the laser beam emission performance.